A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important...A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important for the quality of the nanotubes grown.There is a temperature range of 1000-1500 K in which the narrow armchair single-wall carbon nanotubes can grow rapidly via adduction of C2 dimers,even without the existence of catalysts.The narrow zigzag tubes cannot keep open-ended growth.If the feedstock consists of various species of carbon clusters,the tubes cannot keep open-ended growth.At higher temperatures,the narrow nanotubes close rapidly in the noncatalytic environment,and the products grown are fullerene-like capsules.展开更多
Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of g...Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of grape and of tomato all have a common feature.The leading edges of these broad spectra indicate that some of the penetrating ions pass through the thick targets easily and only lose a small fraction of their initial incident energy.Rutherford backscattering spectrometry and electron microprobe measurements are used to determine the argon concentration in multilayer samples of the seed coat of maize implanted by 200 keV Ar^(+)ions.The results show that about 10%of the Ar^(+)ions can penetrate deeper than~100μm in these samples.展开更多
This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator...This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator is composed of a 4 cm diameter silica waveguide. By testing at D1550 nm, the FSR, FWHM and the depth of resonance are 3122 MHz, 103.07 MHz and 0.8 respectively. By using a polarization controller, the resonance curve under the TM mode can be inhibited. The depth of resonance increased from 0.8 to 0.8913, namely the finesse increase from 30.33 to 33.05. In the experiments, there is an acoustic-optical frequency shifter（AOFS） in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for the counterclockwise lightwave; the frequency difference between the driving frequencies of the two AOFS is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed. The slope of the linear fit is about 0.330 m V/（°/s） based on the 900 to 900 k Hz equivalent frequency and the gyro dynamic range is ±2.0×10^3rad/s.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.59972017the Education Ministry of China.
文摘A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important for the quality of the nanotubes grown.There is a temperature range of 1000-1500 K in which the narrow armchair single-wall carbon nanotubes can grow rapidly via adduction of C2 dimers,even without the existence of catalysts.The narrow zigzag tubes cannot keep open-ended growth.If the feedstock consists of various species of carbon clusters,the tubes cannot keep open-ended growth.At higher temperatures,the narrow nanotubes close rapidly in the noncatalytic environment,and the products grown are fullerene-like capsules.
基金Supported by the National Natural Science Foundation of China under Grant No.19890300by the Foundation for Doctoral Education Programs from the Education Ministry of China under Grant No.96042208.
文摘Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of grape and of tomato all have a common feature.The leading edges of these broad spectra indicate that some of the penetrating ions pass through the thick targets easily and only lose a small fraction of their initial incident energy.Rutherford backscattering spectrometry and electron microprobe measurements are used to determine the argon concentration in multilayer samples of the seed coat of maize implanted by 200 keV Ar^(+)ions.The results show that about 10%of the Ar^(+)ions can penetrate deeper than~100μm in these samples.
文摘This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator is composed of a 4 cm diameter silica waveguide. By testing at D1550 nm, the FSR, FWHM and the depth of resonance are 3122 MHz, 103.07 MHz and 0.8 respectively. By using a polarization controller, the resonance curve under the TM mode can be inhibited. The depth of resonance increased from 0.8 to 0.8913, namely the finesse increase from 30.33 to 33.05. In the experiments, there is an acoustic-optical frequency shifter（AOFS） in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for the counterclockwise lightwave; the frequency difference between the driving frequencies of the two AOFS is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed. The slope of the linear fit is about 0.330 m V/（°/s） based on the 900 to 900 k Hz equivalent frequency and the gyro dynamic range is ±2.0×10^3rad/s.
